"What is life? It is the flash of a firefly in the night. It is the breath of a buffalo in the wintertime. It is the little shadow which runs across the grass and loses itself in the sunset."

Scientists calculate that the number of humans ever to have been born is just over 107 billion. Just seven billion of those are still alive according to the UN's October 2012 estimate of the world's population. So, where did the 100 billion all go, and where will the rest of us go when it's our turn to follow them? Children openly ask these questions with no hint of irony or embarrassment. Adults often only do so in their own minds unheard by anyone else. Blogs for Christian women generally address this issue in a Christian sense, but this is a topic that has engulfed human minds of all faiths and creeds for thousands of years.

The human quest to know why we are here and where we are going was beautifully exemplified by Chief Crowfoot in what were purportedly his last words:

"What is life? It is the flash of a firefly in the night. It is the breath of a buffalo in the wintertime. It is the little shadow which runs across the grass and loses itself in the sunset."

Whether you are one of those people who believes in an existence beyond the physical (maybe even one that includes a supreme being), or are more like those who agree with Richard Dawkins, the evolutionary biologist and proclaimed atheist, you probably accept that we never entirely cease to exist. The first group believes that each of us is a nonphysical entity temporarily attached to a material body, and that the nonphysical part lives forever regardless of what happens to the physical part. The second group holds that each of us is nothing more than the physical body and that the essential "me" or "you" dies with the death of that body.

Both groups agree with the fundamental law of physics, which states that matter - the mass/energy substance of the universe (which started with the Big Bang) - never ceases to exist and that no new matter is ever created. So, our bodies' atoms and molecules have existed since the beginning and will continue to exist in some form (if only "pushing up daisies") for as long as the universe exists.

Many believe that claiming nothing is valid unless it can be explained by science is illogical and limiting. They say that science cannot answer most of the fundamental questions existence poses, and often cite three examples to illustrate this: What caused the Big Bang? What banged? How did the "stuff" that banged come to exist? Science doesn't know and is inclined to dismiss the questions as absurd. Indeed, from a scientific point of view, they probably are.

Similar questions posed by the first group include: When I talk of "me" or "I," where is the "I" located? Is it located somewhere in my body - in my brain, perhaps? Wherever it is, I know it exists because I have self-awareness. This makes a human quite different from a machine, which may be able to perform astonishing feats, yet, is no more aware of itself or anything else than a rock is. Neither the machine nor the rock is conscious, and science has no definitive explanation for consciousness.

Both groups, however, agree that human consciousness or human self-awareness exists, but differ in their definitions of it. Some suggest that when our evolving brains reached a certain degree of physical complexity they acquired the level of human consciousness we now have. They say that our consciousness is a purely physical and inevitable result of that complexity. Most of this group expects scientists to eventually make an artificial brain at least as complex as the human brain, and that it too will have consciousness.

The other group disagrees and holds firmly to the view that no matter how smart machines become they will never be conscious or have self-awareness simply because consciousness is not a physical entity, but is, for want of a better word, spiritual. Furthermore, most of this group believes that we control our decisions - that we have free will, whereas most of the other group believes in causality - that prior events cause subsequent events. Many of this group believes that we have little or no control over events, and that what happens to us and to the entire universe is the inevitable consequence of what happened before - that free will is an illusion.

Some of the first group believes that evolution and spirituality, and indeed creationism, are not necessarily mutually exclusive. They contend that an infinitely intelligent being could have set the ball rolling with the Big Bang, so to speak, and left the rest to evolution.

Both sides may never agree, but one thing is certain: So much of human existence and the workings of the universe are unexplained and probably unknowable that anyone who disagrees that "many explanations are possible" had better have a very good argument to back it up. Maybe the ultimate answer is that all 107 billion of us humans will eventually meet and discover that understanding everything is simple and effortless when you are a spirit no longer encumbered with a physical body. In the meantime, it looks like we will just have to wait and see.